The present invention relates to acoustic apparatus and methods for measuring the flow rate of a fluid by measuring propagation times of ultrasonic signals transmitted through the fluid.
Ultrasonic transit time flow sensors, also known as time of flight ultrasonic flow sensors, detect the acoustic propagation time difference between the upstream and downstream ultrasonic transmissions resulting from the movement of a flowing fluid, which may be a liquid or gas, and process this information to derive a fluid flow rate. Increasing the effective flow rate measurement distance along the flow axis between transducers generally provides a longer measured time interval and, correspondingly, a more precise measurement. On the other hand, size constraints and signal strength considerations motivate a designer to use smaller flow meters with a correspondingly shorter measurement distance. Therefore, there is a need for a time-of-flight flow sensor in which the effective flow rate detection distance between transducers is increased for a specified flow meter size.